It makes sense comparing Yamaha RX-V377 vs Yamaha RX-V671 because they both are able to give some premium features.
A significant difference between the receivers in the number of channels, Yamaha RX-V377 has 5.1 versus 7.1 for Yamaha RX-V671. Regarding power, then RX-V377 has such a W/Ohm ratio - 100/8, 135/6 when RX-V671 has a power of 90/8, 150/4. The THD is the same and is 0.09%.
Competitors' digital to analog converter (DAC) is identical to Burr-Brown 192 KHz/24-bit. Only the RX-V671 supports Bi-amping feature. Each of the AV receivers can transmit an audio signal directly to the amplifier and bypasses any DSP processing.
Both models do not have WI-FI support. Only the RX-V671 has Bluetooth support. Each of these units does not support Apple Music. Competitors do not have built-in Spotify service.
HDR is not available on each model. Compared AV receivers retain the quality of 4K/60Hz signal when transmitting from a source to a TV or projector. HDMI signal transmission in standby mode is implemented in each of the devices. The RX-V671 can scale the input HDMI signal, unlike the RX-V377. The HDR standard - Dolby Vision is not supported by these receivers.
The Yamaha RX-V377 has 4/1 HDMI inputs/outputs versus 6/1 HDMI connectors of the Yamaha RX-V671. The HDMI Audio Return Channel (ARC) feature supports both devices. Unfortunately, HDMI eARC is not available on monitored devices. The Consumer Electronics Control (CEC) feature is present in most modern AV receivers and the models in our comparison are no exception. Both models support the standard HDCP 2.2. The RX-V671 has a built-in phono stage for connecting a vinyl player. A voice control is not available. An ECO mode is only available for the RX-V377. The setup assistant will help you configure Yamaha RX-V377.
None of the rivals equipped with Dolby Atmos multichannel audio decoder. The receivers do not support the surround sound technology DTS:X.